1. Field of the Invention
This invention relates to dissipating heat generated by heat emitting components.
2. Background Art
As the desire for more intensive electronic applications increases, so does the demand for electrical systems that operate at faster speeds, occupy less space, and provide more functionality. To meet these demands, manufacturers design modules containing numerous components with different package types, such as integrated circuits (ICs), multi-chip modules (MCMs), hybrids, and the like, residing in relatively close proximity on a common substrate, for example, a printed circuit board (PCB). Certain components residing on the PCB, such as a central processing unit (CPU) or processor, generate large amounts of heat which must be dissipated.
Generally, heat is dissipated by transferring the heat to a heat-sinking medium such as air or water. Due to the expense and complexity associated with liquid media and, in many cases, the non-availability of such media, it is desirable to use air as a sinking medium. Heat-transfer from the heat source to the surrounding air is accomplished via direct contact between a component and the surrounding atmosphere, passive thermal transfer schemes (e.g., heat pipes), or active liquid cooling systems (e.g., a closed loop circulating cooling system) or a combination of these schemes. In the case of direct contact, heat transfer is generally enhanced by placing a thermally conductive heat sink with protruding fins in contact with an area of high heat flux, such as the upper surface of a component's package or the component's “face.” The heat sink fins greatly increase the heat transfer area to the surrounding atmosphere and reduce the thermal resistance between the heat source and heat sink. Typically, the surrounding air circulates over the heat sink fins by convection; however, in order to further enhance the heat transfer to the surrounding atmosphere, a fan may be used to mechanically move air over the heat sink fins.
In order to enhance the transfer of heat within the heat sink itself, some heat sinks include one or more heat pipes. Other heat sinks are attached to a separate housing having one or more heat pipe. Heat pipes provide a thermally efficient conduit for transferring heat from small areas of high heat generation uniformly throughout the heat sink in order to create a nearly isothermal surface on the heat sink.
In the prior art, an individual heat sink is typically adhesively bonded (e.g., with a thermosetting, conducting epoxy) and/or mounted adjacent to the face of a single heat-generating component with fastening devices (e.g., clips, retaining rings, press fits, or the like). For a computer having a reasonable number of components, with ample height and spacing available, the prior art use of such heat sinks and fastening devices is usually effective for transferring heat away from the critical components of a circuit board.